1. Field of Invention
The present invention relates to a vertical handoff method and system in WALN/3G integrated networks for reducing handoff latency and data loss during vertical handoff.
2. Description of Related Art
Although 3G (third generation) network can cover almost everywhere and a bunch of services are provided at cheaper price. However, a lower-cost and higher bandwidth WLAN (Wireless Local Area Network) network is a still better alternative. 3G network has a wide coverage range but a low transmission speed. On the contrary, WLAN network has a narrow coverage range but a high transmission speed. WLAN and 3G networks are complementary to each other.
Owing to more convenient and less expensive applications, the 3G network services are getting popular than ever. Besides, the WLAN infrastructures are built ubiquitously. The integration between the WLAN system and the 3G system is unavoidable.
A user equipment (UE) may move or roam between the WLAN network and the 3G network during the UE accesses 3G data services. This is called “vertical handoff”. When a vertical handoff occurs, the UE hopes to continue the 3G data services. However, during the UE roams into 3G network, a gateway takes some time in rebuilding connection to the UE. If the rebuilding process takes long time, handoff latency and packet loss may occur and the 3G data services provided to the UE may be interrupted.
In order to minimize packet loss and handoff latency, it needs a practical method and system for reducing handoff latency when UE roams between the WLAN network and the 3G network.